Hello, could anyone recommend a suitable repair to stripped 3/16" BSF threads on a 50's M33?
Many thanks.
Cheers
Dave
a few options.
1. a helicoil may work, normally on alloy/ aluminium depending on thickness .
2. open out, fit a larger plug and re drill and tap to size.
3. make a modified bolt.
4. if thin section, may be a sheet metal rivet system with internal thread, I use them on metric holes dont know if there are British options.
a picture of problem hole may help more.
Thanks Chaz, it is the perimeter screw on the steel chain case. So a sheet metal rivet may well be the answer. I'll look them up, a 4 or 5mm may do it.
Regards.
There's a thing called a Rivnut, does anyone have experience of these?
Cheers
rivnuts are an option to helicoils BUT, you may not be able to find BSC/BSF ( more or less the same both 26tpi) you may be able to use the M6 option and tap out to 1/4. 1/4" is 0.250" M6 is 0.236" so room and pitch similar. 26tpi is 0.038" pitch, M6 x 1 pitch is 0.039".
they are splined so have to be pressed in, as long as the inital hole is to the required size and tolerance they are ok, if tight can be opened out carefully BUT if bigger the splines wont grip.
the down side of rivnuts is that they have flanges, ie larger heads, you may have to counterbore the tops.
hekicoils, you drill out to size, tap thread and fit inside, no flange and can be fitted into blind holes as well as through holes, and available in the right thread.
Thanks Chaz, I will ponder on these options for a while before coming up with a final decision. It may be a week or two, I'll keep you posted.
Kind regards.
Dave
Hi Dave,
I have used Rivet nuts with success, this type not with the spline:
https://www.orbitalfasteners.co.uk/products/m10-rivet-nut-flanged-steel-grip-range-5-50-8-0mm-hole-size-12-1mm
As its on a chain-case is it possible to grind the threaded portion off and silver solder a new nut in place?
Best wishes...
Hi Bess, I managed to source some of these inserts locally yesterday with the insert tool @ £26; but didn't commit to buy just yet. A friend suggested tapping the 3/16" stripped hole out to 5mm. I did this and it seems to work, it just adds the complication of mixing threads. As I was hoping to do the repair with case fitted, it will have to wait until I can solder on new nuts.
Regards and many thanks.
Dave
Tapped out the stripped threads to suit 5mm metric. I'll see how this goes.
Cheers
Dave
Note re chain case: a new gasket was made using a cork/rubber material. Quite thick this, about 4mm. Now refitted the chain case is holding oil and seems good. Had a couple of short runs out and still oil tight.
Phew.
p.s. actually managed to start first kick yesterday!